I am making a 3D house cake for a friend's party.  I have stacked 3 layers (each 1/2 of 9x13) and made the fourth half into a triangle shape ... like I saw in another thread..(see picture)

I have my test run crumb coated my fridge now and it seems stable, but just wondering if you think it needs more support (I just found out the real one will need to travel about 2 hours by car to destination!) Cake is approx about 6" high.  Also, my plan is to use mostly RBC (with fondant texture mats) to decorate the exerior since I don't like the taste of fondant... but I need to make sure it stays on well!

Any tips, suggestions most appreciated!

i would have put support in there somewhere because it's a sculpture -- in some cases 6" can go it alone but then again rule of thumb is every 4" you need support -- but there are tons of 5 and 6" tiers without support --

but i would not let that out my door w/o support --

ohhh good -- i just re-read and this is your test -- oh good!

but i've never been successful using rbc -- rolled buttercream right?  as a cake cover so good for you --

 i think i'd just support the roof if the first three layers are just a little over 4"

Thanks... so I'd cut the board size of roof and then dowels/strawsin the "house" layer?

you'd want the board just under the size of the floor of the attic by a quarter inch all the way around -- you don't want to come into contact with it when you're smoothing/icing/fondanting -- straws/dowel cut the exact same size to each other -- only one inserted into cake to get the right measurement -- yes dowel in the house part --

you got it

I did one of these, and what I learned...

I wish I had put the roof part on a larger board, so it slightly overhangs to make "eaves" on the house. Add and extra 1" or so to each side, or 3 of the 4 sides, leaving the front flat. 

Interesting...Are you taking from an aesthetic point or a structural point?

Both! It works like a "cake board" for the support of the top few layers that make up the "roof". Then the board itself  (exposed sides only) was covered with fondant for "eaves". I did it that way to transport from Texas to Michigan. 

I added one more "clapboard" white strip to join the top to the bottom. Yes, fondant. I know you want butter cream, but I like the added "dimension" given when adding "eaves". I only did it on two sides (the extra inch), so the eaves went with the shape of the cake. No extra inch on the back, nor the front.

Emergency fast cake for family cake muggles, so I didn't go crazy on the details. Not my cleanest work. but it shows the house detail well.

I love your doghouse, Johnson!  Snoopy would be proud and I'll bet the cake muggles were thrilled. 

Thanks Apti. (disclaimer- a "CC stolen" design). Just don't remember whose....

It was short notice, long flights with plane change, and a PITA as far as timing. Given what I had to work with, I was happy. But like all designs, I would do it differently the next time. 

I just needed to post it to help explain to the OP if she wanted to add "eaves" to her pending design. (I actually did it this way to be sure the fondant wouldn't slip off the roof in transit...lol

Thanks everyone for your replies..

I am still a bit confused on "cake rules"

Basic rule is every 4" needs a board and dowels, right?

How do people stabilize those 6 layer rainbow cakes that are definitely more than 4"?  I've seen some people put in a center dowel without a board, but how does that secure it?

And if you have a cake like "my house" would you need a center dowel or is the base dowels and board enough to stabilize?  Could you stabilize it like some people do the rainbow cakes with only a center dowel?

Sorry for so many questions... just trying to understand the how and whys of cake building!

"Rules" are affected by transport method and time, and even cake recipe.

My house only had 4 bubble tea straws to support the "roof" part. No center dowel. BUT, I was the only one touching it, it would be displayed a short time, and it was fully chilled, and I know my cake is sturdy (not very crummy).